Why is iperf (udp, even using multiple threads) slower than piping dd through netcat via ethernet?

Why don’t I see the same performance drop as with tcp or dd through the gateway+infiniband?

Isn’t GigE supposed to scale to line rate a little easier these days now?
Shouldn’t one be seeing something closer to 100MB/s even w/o using Jumbo frames?

It’s not like the hardware I put in use is low-end…

Next step will be retesting via an Infiniband back-to-back link w/o the gateway and then replacing the infiniband-attached server by a faster one. And the iptables firewall on the test “client” will also need a second look.

edit:Thanks to teq on #freebsd.de for pointing out to me that 650MBit/s actually equals the 80MB/s I had measured with dd.